Can less be more? Organ preservation strategies in the management of rectal cancer

Background

Total mesorectal excision (tme) is the current standard of care for the treatment of rectal cancer. However, that surgery is associated with significant morbidity and mortality. Clinicians and patients are seeking alternatives to radical resection. Currently, prevalent organ-sparing strategies under investigation include local excision and nonoperative management (nom).

Methods

We reviewed the current evidence in the literature to create an overview of the use of transanal endoscopic surgery and watch-and-wait strategies in the modern management of rectal cancer.

Results

Compared with radical resection, transanal endoscopic surgery in patients with early rectal cancer (cT1) having favourable histopathologic features is associated with an increased risk of local recurrence, but no difference in 5-year survival. In patients with T2 or early T3 cancer, strategies that use neoadjuvant or adjuvant therapy as adjuncts to local excision are under evaluation. Nonoperative management is a new option for patients who experience a complete clinical response after neoadjuvant chemoradiotherapy (ncrt). The selection criteria that will appropriately identify patients for whom nom will succeed are not established.

Conclusions

Local excision is appropriate for early rectal cancer with favourable histopathologic features. Although organ-preserving strategies are promising, the quality of the evidence to date is insufficient to replace the current standard care in most patients. Patients should be offered nom in the safe setting of a clinical trial or registry. Rigorous follow-up, including endoscopy and imaging at frequent intervals is recommended when radical resection is forgone.

Resveratrol mainly stimulates the glycolytic ATP synthesis flux and not the mitochondrial one: a saturation transfer NMR study in perfused and isolated rat liver

Our aim was to monitor the effects of resveratrol (RSV) on the respective contribution of glycolysis and oxidative phosphorylation on the unidirectional flux of ATP synthesis in whole isolated rat liver perfused with Krebs-Henseleit Buffer (KHB). The rate of tissular ATP supply was measured directly by monitoring the chemical exchange Pi toward ATP with saturation transfer (ST) (31)P nuclear magnetic resonance, a method applied for the first time for studying the effects of RSV. ST allows the measurement of the total cellular Pi→ATP chemical exchange; after specific inhibition of glycolysis with iodacetate, ST could provide the Pi→ATP flux issued from mitochondria. This latter was compared to mitochondrial ATP turn-over evaluated after chemical ischemia (CI), performed with specific inhibition (KCN) of oxidative phosphorylation, and measured by standard (31)P NMR spectroscopy. In controls (KHB alone), the apparent time constant (ks) of Pi exchange toward ATP as measured by ST was 0.48±0.04s(-1) leading to a total ATP synthesis rate of 37±3.9μmolmin(-1)g(-1). KHB+RSV perfusion increased ks (+52%; p=0.0009 vs. KHB) leading to an enhanced rate of total ATP synthesis (+52%; p=0.01 vs. KHB). When glycolysis was previously inhibited in KHB, both ks and ATP synthesis flux dramatically decreased (-87% and -86%, respectively, p<0.0001 vs. KHB without inhibition), evidencing a collapse of Pi-to-ATP exchange. However, glycolysis inhibition in KHB+RSV reduced to less extent ks (-41%, p=0.0005 vs. KHB+RSV without inhibition) and ATP synthesis flux (-18%). Using the CI method in KHB and KHB+RSV, KCN addition after glycolysis inhibition induced a rapid fall to zero of the ATP content. The mitochondrial ATP turnover R(t0) and its time constant kd mito were similar in KHB (1.18±0.19μmolmin(-1)g(-1) and 0.91±0.13min(-1)) and KHB+RSV (1.36±0.26μmolmin(-1)g(-1) and 0.77±0.18min(-1)). Since mitochondrial ATP turnover was not increased by RSV, the stimulation of Pi-to-ATP exchange by RSV mainly reflected an increase in glycolytic ATP synthesis flux. Moreover, the maintenance by RSV of a high level of Pi-to-ATP exchange after glycolysis inhibition evidenced a protective effect of the polyphenol, in agreement with our previous hypothesis of a stimulation of substrate flux throughout the glycolysis 3-carbon step.